We move on to the race for the white house. In you polls showing a big convention bounce for Hillary Clinton as Donald Trump doubles down in his fight with the Muslim parents of a fallen soldier and steps up attacks on Hillary Clinton. Comparing her now to the devil. ABC's Tom llamas is on the trail with trump in Harrisburg, Pennsylvania. Good morning, Tom. Reporter: George, good morning to you. Donald Trump calling Hillary Clinton the devil is a first and this comes at the same type he's in the middle of a growing fight with fellow republican, billionaire, even the president over a back and forth with the family of a fallen U.S. Soldier. Overnight, Donald Trump warning of the possibility of a rigged election. And I'm telling you, November 8th we better be careful because that election is going to be rigged and I hope the republicans are watching closely or it's going to be taken away from us. Reporter: At a campaign event in Pennsylvania he took his attacks on Hillary Clinton to a diabolical level, saying this of senator Bernie sanders' endorsement of Clinton. But he made a deal with the devil. She's the devil. Reporter: But it's trump's attacks on a gold star family that spoke out at the democratic convention that continue to get him in trouble. Have you even read the united States constitution? Reporter: Senator John McCain calling out trump saying just because trump is the gop nominee doesn't mean he can, quote, defame those who are the best among us, and the vfw veterans group saying to ridicule a gold star mother is out of bounds. Trump's running mate governor Mike pence put on the spot during a town hall by a mother whose son serves in the U.S. Air force. Will there ever be a point in time to look trump in the eye and tell him enough is enough? Reporter: That mother getting booed from others at the town hall for asking her question. Captain khan is an American hero. And we cherish, we cherish his family. We cherish all of our gold star families. Reporter: President Obama also alluding to the controversy praising all the gold star families. That our gold star families have made a sacrifice that most of us cannot even begin to imagine. Reporter: And fellow billionaire Warren Buffett who's supporting Hillary Clinton saying this about trump. Have you no sense of decency, sir? Reporter: Still trump says he has a right to defend himself. Horrible things were said about me. I think it was, frankly, very tough so all I did is respond and I will always respond. Reporter: As trump fighting with that gold star family "The New York times" has a front page investigation looking into the numerous deferments, draft deferments during the Vietnam war by Donald Trump, mostly for education but one of them for bone spurs in his heels. Now, this came at a time when trump was a very active athlete and had just picked up the game of golf, trump has said that condition has since healed and he has acknowledged some guilt for not serving.

This transcript has been automatically generated and may not be 100% accurate.

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